1. Field of the Invention
The present invention relates generally to a power switching apparatus and, more particularly, to a power switching apparatus for transmitting driving force created by one driving power source to two systems of gear groups by changing the direction of rotation.
2. Description of the Background Art
Unlike a facsimile machine of a separate type having separate structures for transmission and reception, a facsimile machine capable of both transmission and reception has advantages that not only the entire apparatus can be made compact and less costly but also operation noises and power consumption can be reduced, and maintenance thereof can be simplified since driving means and structures supporting the driving means can be shared for transmission and reception.
FIGS. 6A and 6B are views showing a rotating transmission structure which can be incorporated in such a facsimile machine, etc., which is disclosed in Japanese Patent Laying-Open No. 61-184248.
Referring to the figures, the structure and operation thereof will be briefly described.
As shown in FIG. 6A, a driving motor 102 normally rotates to cause a worm 103 to rotate in the direction of arrow a, thereby rotating a sun gear 107 in the direction of arrow b. The rotation of the sun gear 107 drives a swinging arm 110 friction-coupled thereto to swing in the direction of arrow c to a first position, thereby engaging a second transfer gear 115 with a first gear 119, so that the gear 119 is rotated in the direction of arrow d. When the driving motor 102 is reversely rotated, as shown in FIG. 6B, the worm 103 is rotated in the direction of arrow e to rotate the sun gear 107 in the direction of arrow f. The rotation of the sun gear 107 then drives the swinging arm 110 friction-coupled thereto to swing in the direction of arrow g from the first position to a second position, thereby engaging a first transfer gear 113 to a second gear 121, so that the gear 121 is rotated in the direction of arrow h. The first and second gears 119 and 121 are coupled to two systems of gear groups, respectively, and, therefore, each being rotated, drive the respective gear groups to rotate.
In such a structure, even with one driving power source (the driving motor 102), the transmission system of rotating movement can be changed by shifting the direction of rotation thereof, to adapt to transmission operation or reception operation by a facsimile machine, etc.
In other words, a power switching apparatus is implemented by driving a sun gear to rotate by power generated by a motor, providing transfer gears to be engaged to the sun gear pivotally around an arm disposed around the rotating axis of the sun gear which can swing freely and by providing a pair of driven gears at a distance apart from each other in the circumferential direction of the sun gear.
The sun gear 107 is driven to rotate in one direction in a time period W1 as shown in FIG. 7, so that one of the driven gears 119 is driven to rotate, thereby feeding an original for transmission, while at the time of reception the sun gear 107 is driven to rotate reversely in a period W2 to carry a sheet of recording paper, thereby driving the other driven gear 121 to rotate. When the sun gear 107 is driven to rotate in one direction, the driven gear 119 is driven to rotate with a time delay of .DELTA.W1, shown in FIG. 6. The time .DELTA.W1 is time required for the transfer gear 115 to be engaged with the driven gear 119. When the sun gear 107 is rotated reversely, the other driven gear 121 is driven to rotate with a time delay of .DELTA.W2. The time delays .DELTA.W1 and .DELTA.W2 vary in accordance with the angular position when an arm 110 stops, which varies due to frictions and so forth. The time .DELTA.W1 and the time .DELTA.W2 fluctuate accordingly.
Such fluctuation in time delay gives rise to the following problems in a conventional power switching apparatus.
In a facsimile machine capable of both transmission and reception, if an original is carried after .DELTA.W1 elapse since a sun gear is driven to rotate to read the original, for example, variation in this time delay .DELTA.W1 causes a change in time of the original to be carried arriving at a reading head. This causes variation of reading initiation time accordingly. It is desired to transmit the original image accurately by advancing the reading initiation time at the tip of the original. Such time delays .DELTA.W1 and .DELTA.W2 in the operation of the respective driving gears are desirably constant not only in the facsimile machine both capable of transmission and reception as described above but also in any other apparatuses having such a power switching structure.